1. Field of the Invention
The present invention relates to automated mailing systems and more particularly to a keyboard actuated electronic mailing system wherein the functions accessible by the keyboard can be changed.
2. Description of the Prior Art
Typical electronic postage scales can be broken down into four basic subsystems. These are the mechanical scale, the keyboard and display, the scale and system processor ("main processor"), and an interface for peripheral devices. The heart of the system is the main processor which includes software sometimes known as the "main line code". It is the main line code which directs the scale functions.
In prior postage scale designs, keyboard decoding was performed by the main processor. Thus, the main line code was used to determine which machine function corresponded to a particular key which has been actuated. Although these systems perform adequately, they suffer from the limitation that in order to change the functional designation of a particular key or keys on the keyboard, the main line code has to be altered. Such a software change is undesirable for several reasons. First, the alteration of any subroutine(s) within the main line code is complicated by the fact that the entire operation of the main line code after the change generally has to be verified by rather rigorous testing. Second, since the main line code is resident in the main processor, it is not easily altered. Third, once a particular functional keyboard layout has been programmed within the main line code, the layout cannot be temporarily changed (e.g., by a technician) to provide alternate functions or a different keyboard layout.
In U.S. Pat. No. 3,602,894, a key-entry system is disclosed which has different program keys for selecting a plurality of programs. The functions of the keys, however, remain fixed, although the program that is executed at any given time is changeable.
U.S. Pat. No. 4,080,659 teaches the use of a calculator having a replaceable ROM programming assembly for use in calculating and filling out personal income tax forms. A keyboard is provided which includes standard numerical digit and arithmetic function keys. Some of these keys are operable only when the calculator is in an arithmetic operation mode, but none of the key functions changes upon replacement of one ROM for another.
Another prior art system is disclosed in U.S. Pat. No. 4,145,742. A programmable calculator employs modular read-write memory and ROM units for storing programs and data. In addition to fixed value keys, the keyboard includes certain specified definable keys for calling up user-defined or preprogrammed subroutines. The additional key functions are obtained by the replacement, in whole or in part, of the mainline program stored in the calculator. With the insertion of appropriate ROM units, all users have access to the functions defined thereby.
A typical electronic postage meter is disclosed in U.S. Pat. No. 3,978,457 entitled "Microcomputerized Electronic Postage Meter System" issued Aug. 31, 1976 to Frank P. Check, Jr. et al and also assigned to the assignee of the present invention.
Another postage calculator is disclosed in U.S Pat. No. 4,139,892. In the system disclosed in this patent, a postage scale is used in conjunction with random access memories (RAM) and programmable read-only memories (PROM) to perform a weighing operation. The postage calculation operation and a data display operation proceed according to various keyboard entries. Typical keys on a postage scale keyboard are the numerical keys from 0 to 9, postal rate keys designating various types of postage service (e.g., surface mail, airmail, first class, book rate), and special service keys (e.g., registered, special delivery, C.O.D., certified).
It would be advantageous to provide a system where the format of a keyboard can be readily changed so that the functions initiated by different keys can be swapped to suit a particular user's needs or preference.
It would also be advantageous to provide a system wherein the set of functions that can be accessed by the system keyboard can be readily changed without replacing all or part of the mainline program. In such an instance, the system itself would be capable of performing any one of a master set of functions. The system keyboard would then be customized to provide any desired subset of those functions which a user requires. The ability to change the functions accessible by the system keyboard, without having to change the mainline program, should be available to a service technician so that the keyboard functions can be readily changed in the field.
As hereinabove mentioned, the ability to change keyboard formats and/or functions should be available without the need for changing the mainline code which is resident in the main processor. Such a system would enable a service representative to change the subset of functions which the system keyboard can access so that specific service functions, not available to the regular system user, can be performed.